1. FIELD OF THE INVENTION
The present invention relates to load frames and in more particularly to means for reacting side loads between the upper and lower cross heads or platens of a load frame.
2. PRIOR ART
In the prior art, the assignee of the present invention, MTS Systems Corporation of Eden Prairie, Minnesota has been engaged in making and selling various multiple column load frames for various uses.
For example, the corporation is the owner of U.S. Pat. No. 3,442,120 which shows a resonant hydraulic fatigue testing device utilizing a load frame with upright columns, wherein suitable hydraulic clamps can be used on the smooth columns (or other types of clamps if desired). Such clamps are conventionally used and have been used for many years.
Heavy load frames having four columns, one on each of the corners of a square or rectilinear base, and having a movable cross head mounted on the columns have also been widely used.
The columns used between the platens adequately carry the vertical loads (parallel to the axes of the columns), and are capable of reacting side loads caused by specimen misalignment. Typical side load capability for load frames is less than ten percent of the axial load. Stress and deflection of the columns in horizontal direction (assuming that the columns are vertical) can thus be a problem when testing specimens that require substantial biaxial loading.